the blind spot in our eyes, what is the reason for its exsistance?
2007-03-22 06:48:44 · 6 answers · asked by angy_4ever2003 2 in Science & Mathematics ➔ Zoology
The inner layer of the eye, or retina, is composed of small nerve cell bodies, rods and cones, that detect and transmit to the brain images of light. They cover the inner surface of the eye but are missing in the area where the optic nerve comes into the eye. This spot also is where blood vessels enter the eye. In other words, there has to be a spot where blood can enter to supply nutrients to the cells of the retina, and where the axons from the rods and cones can be gathered together, so to speak, to travel in one cord back to the brain. So this area is a "blind spot." However, you make up for that area by vision in your other eye.
2007-03-22 06:57:41 · answer #1 · answered by Ivan 3 · 1⤊ 0⤋
The nerves carrying the signals from the retina come out of the front of the retina and so have to go through it as the optic nerve to reach the brain. That's just the way human eyes evolved. Squid eyes are more logical. The nerves come out of the back of the retina and thus squid do not have a blind spot. Eyes are such useful devices, they have evolved about 40 different times which is why there is such a diversity of them.
2007-03-22 21:06:05 · answer #2 · answered by tentofield 7 · 0⤊ 1⤋
The blind spot is where the optic nerve leaves the eye to go to the brain. At that point on the retina (at the back of the eye), there are no light receptors - only nerve fibers - so you can't see anything.
2007-03-22 13:59:12 · answer #3 · answered by jesusislord_514 3 · 0⤊ 0⤋
to refute the claim of intelligent design in humans....
the receptors in the eye point away from the center of the eye. the nerve fiber from each receptor are collected in a bundle which has to go somewhere through the receptor layer to reach the brain.
The reason it is constructed this was comes from how the eye develops. The neural tube forms a cuplike structure, which will form the eye, so the neurons grow on the inside of the cup. While we can compensate for it, an eye does not have to be designed in this backwards way, as we can clearly see in the case or cephalopod eyes. It just is as a result of our developmental history.
2007-03-22 14:42:39 · answer #4 · answered by convictedidiot 5 · 0⤊ 1⤋
without getting to scientific, and taking a different approach to the question at hand.
people also have blind spots (peripheral vision) because we are predators. predators eyes are facing forward to focus on our prey during a hunt..... versus on each side of our head like prey to watch our surroundings for a potential attack...... even though we're not technically predators any longer, we're not far enough down the evolutionary track from when we once were to make a change, nor are we or ever will be prey, so no need to have them moved to the sides.... plus we look better like this don't you think?
2007-03-22 15:11:49 · answer #5 · answered by brian a 3 · 0⤊ 0⤋
humans evolved eyes from nervous tissue...and basically the wiring is backwards to where your optic nerve is centered in one location that goes to your brain on the back of your retina.....this area on the back of your eye has no rods or cones therefore you have a blindspot
2007-03-22 13:56:30 · answer #6 · answered by dani1elle 2 · 0⤊ 0⤋